A method, composition and filter for reducing the presence of sludge or varnish precursors in a lubricating oil circulating within an internal combustion engine. The lubricating oil containing sludge or varnish precursors is contacted with discrete particles of an oil insoluble, oil wettable compound having an antioxidant functional group and/or a dispersant functional group, which are capable of complexing with sludge or varnish precursors. Preferably the compounds comprises a crosslinked amine having ethylene amine functionality. The starting polyethylene amines have a number average molecular weight in the range of about 100 to about 60,000, preferably 200 to 250 and are crosslinked with a silicon oxide, silane, silicate, epoxide, quinone, or phenol-formaldehyde crosslinking agent. The particles are encaged within a one or two stage oil filter together with filtering media such as chemically active filter media, physically active filter media and inactive filter media.